The present invention relates to spirit levels.
Spirit levels, also called bubble levels, are well known instruments used for setting horizontal or vertical surfaces. The level includes a sealed vial containing an air bubble floating in a liquid. The particular surface is considered horizontal or vertical when the air bubble rests between predetermined graduated marks in the vial.
When setting, also called plumbing, a vertical surface with a typical spirit level, the bubble vial is generally perpendicular to the surface being set, with the result that the air bubble must be viewed from a position which does not directly face the surface being set. Unfortunately, it is sometimes awkward or strenuous to view the air bubble from such a position. Adverse lighting conditions can also exacerbate difficulty in reading the bubble from such a position.
U.S. Pat. No. 4,103,430 to Schrader describes a viewing device for a spirit level including a luminescent panel and a pivotable mirror arranged to provide an illuminated image of the air bubble which may be viewed without having to look directly at the air bubble vial. However, the air bubble must still be viewed from a position which does not directly face the surface being set.
The present invention seeks to provide a novel spirit level wherein the air bubble-may be viewed from a position which directly faces a surface being set.
There is thus provided in accordance with a preferred embodiment of the present invention a spirit level including a body having a level face for setting a surface, at least one bubble vial mounted in the body, the bubble vial having a longitudinal axis generally perpendicular to the level face, and an optical transfer element fixed to the body which transfers an image of the bubble vial to a viewing plane generally parallel to the level face.
In accordance with a preferred embodiment of the present invention the optical transfer element enlarges the image., In accordance with another preferred embodiment of the present invention, the optical transfer element diminishes a size of the image. Illumination apparatus may be provided for illuminating the image.
In accordance with a preferred embodiment of the present invention the optical transfer element includes a reflective surface arranged at an angle to the bubble vial and to the viewing plane and which reflects the image of the bubble vial to the viewing plane. The reflective surface may be a mirror or a prism, for example. In accordance with another preferred embodiment of the present invention the optical transfer element includes an electric viewing device.
The optical transfer element may be internally or externally mounted in or on the spirit level. Additionally, the optical transfer element may be detachable from the spirit level.
In accordance with a preferred embodiment of the present invention the optical transfer element is an add-on accessory which may be attached to the spirit level.
There is also provided in accordance with a preferred embodiment of the present invention a method for facilitating viewing a bubble vial of a spirit level while setting a vertical surface, the bubble vial having a longitudinal axis generally perpendicular to the vertical surface, the method including the steps of fixing an optical transfer element to the spirit level which transfers an image of the bubble vial to a viewing plane generally parallel to the vertical surface, and viewing the bubble in the viewing plane.